1. Field of the Invention
The invention under consideration relates to an electric heating device for heating a flowing medium, wherein, in the context of the invention under consideration, a medium is particularly understood as a liquid medium. In particular, the invention under consideration relates to an electric heating device for a motor vehicle, in this case, especially for a motor vehicle that is operated with a drive that gives off almost no process heat or that does not give off any pertinent quantity of process heat. Particularly included in this group are hybrid drives. Accordingly, the invention under consideration is intended to provide a heating device that is particularly suited for generating the heat that is required for the processes running in individual system parts of a motor vehicle, or at least the heat that promotes such processes. The heating device according to the invention should, in particular, be suitable for generating a larger amount of heat in the shortest time, in order to give off this heat within the shortest time to the corresponding system parts within the motor vehicle. At the same time, some of the attention of the invention under consideration should be given to avoiding overheating of the electric heating device caused by control errors.
2. Description of the Related Art
In the state of the art, it is known to use so-called resistance heating elements or even PTC heating elements in motor vehicles, whereby such heating elements are self-regulating, because these display a greater resistance as the heating increases and consequently allow a lower amount of current through. The PTC heating elements consequently have self-regulating characteristics that prevent these heating elements from overheating. The maximum temperature that a PTC resistor can reach at a given operating voltage can be influenced by certain parameters during the manufacture of the PTC heating elements, which does not have to be explained in more detail here.
PTC heating elements are accordingly routinely deployed in radiators, particularly those that serve to heat the passenger compartment in such vehicles whose drive unit in any case gives off insufficient waste heat for climate control in the passenger compartment.
From DE 39 07 179, an electric heating device with a housing is known, in which a multitude of PTC heating elements are arranged, whereby the liquid medium (in this case, water) that is to be heated flows directly around these PTC heating elements. The electric connecting elements leading to the electric heating elements accordingly lie freely in the medium to be heated, which does not comply with the safety requirements that should be required and that additionally carries the problem of the corrosion of the metallic parts of the connecting elements. Furthermore, the arrangement of the electric heating elements directly in the flow conduit hinders any maintenance and repair work.